Metal Matrix Composites (MMC) is a material which comprises hard particles such as nitrides, carbides, borides and oxides embedded in a ductile metal phase. Typically, the MMC-component is manufactured by subjecting a powder blend of hard particles and a metal alloy powder to Hot Isostatic Pressing (HIP). The properties of the MMC-materials can be tailored for specific applications by adjusting the proportion of the volume fraction of hard particles in relation to the volume fraction of the ductile metal phase. MMC-materials are often used as a wear resistant material in various applications, for example mining. The primary use of MMC as a wear resistant material is for protecting against abrasive wear, i.e. wear from particles or bodies that slide over the surface of a component. Under abrasive conditions the wear resistance of known MMC-material is typically improved by increasing the volume fraction of hard particles in the material.
A problem associated with known MMC materials is their relatively low resistance to erosion.
Erosion is common wear mechanism in which a stream of particles, such as a slurry of sand and water, hits the surface of a component and strikes out small pieces of material from the component. Under conditions where erosion is the dominating wear mechanism, the wear is more complex than under conditions where abrasion dominates. This is to a certain extent due to that the erosion rate of the material in the component is dependent on the impinging angle of the erosive material. In general, the ductile metal phase performs better at high impingement angles whilst the hard and relatively brittle hard particles perform better at lower angles. Hence, the resistance to erosion depends on the individual properties of the hard phase and the ductile phase as well as on the combination of the two phases.
Merely increasing the volume fraction of hard particles in the precursor powder that the component is made of does therefore not necessarily result in reduced erosive wear of the component. An increase of the hard phase would lead to less ductile phase in the component and hence lower erosion resistance at high impingement angles.
A further aspect is that an increase of the volume fraction of hard particles in the precursor powder makes the powder more difficult to mix to a homogenous blend in which a large proportion of the hard particles are surrounded by ductile metal particles. As a result thereof a large portion of the hard particles could be in contact with each other which in turn could lead to networks of interconnecting carbides, thereby making the MMC material brittle and vulnerable to erosion.
Attempts have been made in the past to achieve wear resistant claddings on components by using laser beams to melt a powder of hard particles and cobalt based alloy powders onto the surface of the component. [T. R Tucker et al, Thin Solid Films 118 (1984) 73-84 “Laser-processed composite metal cladding for slurry erosion resistance]. However, the laser based method produces molten phases and during solidification, segregation of alloy elements results in inhomogeneous and brittle areas in the cladding layer. The method is further expensive, time consuming, limited with regards to coating thickness and unsuitable for producing large wear resistant components.
Hence, it is an object of the present invention to present an improved method of manufacturing a wear resistant component. In particular it is an object of the present invention to present a method for manufacturing components with improved resistance to erosive wear. It is also an object of the present invention to present a cost effective method which results in wear resistant components having a homogenous, i.e. isotropic structure. Yet a further object of the present invention is to achieve a component which has high resistance to wear under erosive conditions